The continent was once home to a remarkable and distinctive collection of giant beasts.

These megafauna, as researchers like to call them, included an immense wombat-like animal (Diprotodon optatum) and a 400kg lizard (Megalania prisca).

But all - including the marsupial lion - had disappeared by the end of the Pleistocene Epoch (11,500 years ago).

Some scientists think the significant driver behind these extinctions was climate change - large shifts in temperature and precipitation.

But Dr Prideaux and colleagues argue the Thylacoleo Caves' animals give the lie to this explanation because they were already living in an extremely testing environment.

"Because these animals were so well adapted to dry conditions, to say that climate knocked them out just isn't adequate. These animals survived the very worst nature could throw at them, and they came through it," co-author Professor Bert Roberts told BBC News.

"If you look at the last four or five glacial cycles, where the ice ages come and go, the animals certainly suffered but they didn't go extinct - they suffered but survived," the University of Wollongong scientist said.

This assessment would be consistent with the other favoured extinction theory - extermination by humans, either directly by hunting or indirectly by changing the landscape through burning.

As the name suggests, there are precious few trees on the Nullarbor Plain